The history of intraocular lens implants can be traced to the method of fixation. Initially, intraocular lens implants were of the posterior chamber type developed by Harold Ridley. However, the technical difficulties and complications associated with the Ridley lens lead to a change in the positioning of the artificial lens in the eye. This change resulted in intraocular lenses being placed in the anterior chamber of the eye.
The evolution of anterior chamber lenses developed along two types. The first type is represented by the flexible loop lenses of the Dannheim lens illustrated in West German Pat. No. 1034325 issued to H. Dannheim on July 17, 1958 and entitled "Artificial Eye Lens". The second type of anterior lenses is represented by the Strampelli lens which is of a rigid type in the form of a meniscus ending in a dove tail.
The evolution of the Strampelli lens has resulted in the development of the Tennant lens illustrated in U.S. Pat. No. 4,261,065 issued to J. Tennant on Apr. 14, 1981 and entitled "Artificial Intraocular Lens with Forward-Position Optics". The evolution of the Dannheim lens has resulted in a semi-flexible lens that retains three or four points of fixation represented by the Kelman lens illustrated in U.S. Pat. No. 4,174,543 issued to C. Kelman on Nov. 20, 1979 and entitled "Intraocular Lenses". Futher development of the Dannheim and Kelman type flexible lenses has resulted in a semi-flexible lens with biarcuate fixation in which the fixating members match the curvature of the tissue in which they are affixed. Such a lens is described in U.S. Pat. No. 4,254,510 issued to J. Tennant on Mar. 10, 1981 and entitled "Implant Lens with Biarcuate Fixation".
Although the development of anterior chamber lenses has significantly progressed from the Dannheim and Strampelli types, it has still been found that the most common difficulty with anterior chamber lenses is the necessity to maintain an inventory of various sizes to fit various size eyes and more particularly the diameter of the anterior chamber of the recipient's eyes. In addition, a surgical judgment must be made on the part of the surgeon in determining the size of the anterior chamber in selecting the proper sized lens. An additional problem associated with anterior chamber lenses is that, although flexible lenses have been developed, such lenses do not have the desired ability to maintain lens stability necessary for the lens to be tolerated without destruction of the eye.
The effort for a flexible yet stable lens has its development in the Dannheim lens in which the loops were made of nylon. However, it has been found that these nylon loops dissolved and were unstable, even when freshly implanted, allowing the optic to move readily, forward, backward, or horizontally in the anterior chamber. Material such as polypropylene has been utilized in place of nylon; however, although being less likely to dissolve, polypropylene loops suffered in that such loops caused the position of the optic to be unpredictable and unstable.
Lens fixation loops have also been composed of polymethylmethacrylate (PMMA) material which material is unlikely to dissolve with improved stability over nylon and polypropylene type materials. However, lenses utilizing PMMA for such loops have been shown to be easily distorted which allow these loops to be pressed back out of the angle in which they are intended to reside which causes undesirable iris tucking and increased pressure within the anterior chamber of the eye. It thus has been found that the design of the anterior chamber lens loop fixation members is highly critical to the design of such lenses as these loops engage the anterior chamber tissue such that the centration and stability of the optic is dependent upon the integrity of these fixation loops.
A need has thus arisen for an anterior chamber lens having improved stability within the anterior chamber of the eye to prevent anterior-posterior movement of the optic, torsional movement and posterior migration of the lens within the anterior chamber of the eye. Furthermore, a need has developed for an anterior chamber lens which is flexible to fit within a range of diameters of the anterior chamber of the recipient eye while maintaining its stability and centration.